Anode material and method for producing the same

ABSTRACT

To provide an anode material configured to increase the reversible capacity of lithium ion secondary batteries, and a method for producing the anode material. The anode material is an anode material for lithium ion secondary batteries, comprising a P element and a C element and being in an amorphous state.

TECHNICAL FIELD

The disclosure relates to an anode material and a method for producingthe anode material.

BACKGROUND

In recent years, with the rapid spread of IT and communication devicessuch as personal computers, camcorders and cellular phones, greatimportance has been attached to the development of batteries that isusable as the power source of such devices. In the automobile industry,etc., high-power and high-capacity batteries for electric vehicles andhybrid vehicles are under development.

For the purpose of developing a high-capacity lithium ion secondarybattery, it has been discussed to use phosphorus as an anode activematerial. Non-Patent Literature 1 discloses an all-solid-state batterywhich contains an anode material containing Li, P, S and C elements andin which black phosphorus is used as an anode active material.

Non-Patent Literature 1: M Nagao, et al., Journal of Power Sources 196(2011) 6902-6905

According to Non-Patent Literature 1, a further increase in reversiblecapacity can be expected considering the theoretical capacity of thecase where the charge capacity after initial charging is about 1700mAh/g and phosphorus is used as the anode active material.

SUMMARY

The disclosed embodiments were achieved in light of the abovecircumstances. An object of the disclosed embodiments is to provide ananode material for lithium ion secondary batteries, which is configuredto increase the reversible capacity of lithium ion secondary batteries.Another object of the disclosed embodiments is to provide a method forproducing the anode material.

In a first embodiment, there is provided an anode material for lithiumion secondary batteries, comprising a P element and a C element andbeing in an amorphous state.

The anode material of the disclosed embodiments may further comprise atleast one of a Li element and an S element.

The anode material of the disclosed embodiments may be such that adiffraction peak derived from raw materials is not present in a spectrumobtained by XRD measurement.

In the anode material of the disclosed embodiments, a content of acarbon material containing the C element may be 30 mass % or more.

In another embodiment, there is provided an all-solid-state lithium ionsecondary battery comprising a cathode layer, an anode layer and a solidelectrolyte layer disposed between the cathode layer and the anodelayer, wherein the anode layer contains the anode material.

In another embodiment, there is provided a method for producing an anodematerial for lithium ion secondary batteries, the method comprisingpreparing a phosphorus material and a carbon material, and amorphizingthe phosphorus material and the carbon material.

For the method for producing the anode material of the disclosedembodiments, in the preparing, a first raw material compositioncontaining the phosphorus material and the carbon material nay beprepared by nixing the phosphorus material and the carbon material, andin the amorphizing, mechanical milling may be carried out on the firstraw material composition at a grinding energy of 3.07 B 10¹¹ kJ×sec/g ormore.

For the method for producing the anode material of the disclosedembodiments, in the preparing, at least one selected from the groupconsisting of a lithium material, a sulfur material and a lithium-sulfurmaterial may be further prepared, and in the amorphizing, the phosphorusmaterial, the carbon material and the at least one selected from thegroup consisting of the lithium material, the sulfur material and thelithium-sulfur material, may be amorphized.

For the method for producing the anode material of the disclosedembodiments, in the preparing, a second raw material compositioncontaining the phosphorus material, the carbon material and the at leastone of the lithium material, the sulfur material and the lithium-sulfurmaterial, may be prepared by mixing the phosphorus material, the carbonmaterial, and the at least one selected from the group consisting of thelithium material, the sulfur material and the lithium-sulfur material,and in the amorphizing, mechanical milling nay be carried out on thesecond raw material composition at a grinding energy of 3.07 B 10¹¹kJ×sec/g or more.

According to the disclosed embodiments, an anode material configured toincrease the reversible capacity of lithium ion secondary batteries, anda method for producing the anode material, are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIG. 1 is a schematic sectional view of an example of an all-solid-statelithium ion secondary battery used in the disclosed embodiments;

FIG. 2 is a view showing the XRD patterns of the anode material ofExample 2, the anode material of Comparative Example 2, blackphosphorus, red phosphorus, a lithium-sulfur material(75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr) and acetylene black (AB);

FIG. 3 is a view showing the Raman spectra of the anode material ofExample 2, the anode material of Comparative Example 2, the blackphosphorus, the red phosphorus and the lithium-sulfur material(75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr);

FIG. 4 is a secondary electron image (a SEM image) of the anode materialof Example 2;

FIG. 5 is a backscattered electron image (a BF image) of the anodematerial of Example 2;

FIG. 6 is a secondary electron image (a SEM image) of the anode materialof Comparative Example 2;

FIG. 7 is a backscattered electron image (a BF image) of the anodematerial of Comparative Example 2;

FIG. 8 is an image obtained by EDS mapping of the anode material ofExample 2;

FIG. 9 is an image obtained by EDS mapping of the anode material ofComparative Example 2;

FIG. 10 is a view showing the charge-discharge curves of the evaluationbattery of Example 2; and

FIG. 11 is a view showing the charge-discharge curves of the evaluationbattery of Comparative Example 2.

DETAILED DESCRIPTION

A. Anode Material

In the disclosed embodiments, an anode material for lithium ionsecondary batteries, comprising a P element and a C element and being inan amorphous state, is provided.

In the disclosed embodiments, the term ‘raw material means a rawmaterial for the anode material, which is a phosphorus material, acarbon material or at least one selected from the group consisting of alithium material, a sulfur material and a lithium-sulfur material.

Also in the disclosed embodiments, the term ‘raw material composition isa composition obtained by mixing the raw materials and encompasses afirst raw material composition obtained by nixing the phosphorusmaterial and the carbon material and a second raw material compositionobtained by mixing the phosphorus material, the carbon material and theat least one selected from the group consisting of the lithium material,the sulfur material and the lithium-sulfur material.

It was found that the reversible capacity of a lithium ion secondarybattery is increased by incorporating, in the battery, an anode materialcomprising a P element and a C element and being in an amorphous state.The reason is thought as follows. When the anode material is in theamorphous state, the phosphorus material and carbon material containedin the anode material are uniformly dispersed; therefore, a conductivepath in the anode material is optimized, thereby enhancing thereversibility of lithium dissolution and deposition.

1. P Element

The anode material contains a P element.

The P element derives from the phosphorus material used as a rawmaterial. The phosphorus material is not particularly limited, as longas it is a material containing a P element. As the phosphorus material,examples include, but are not limited to, an elemental phosphorus. Theelemental phosphorus may be at least one allotrope selected from thegroup consisting of white phosphorus (yellow phosphorus), redphosphorus, violet phosphorus and black phosphorus.

In the disclosed embodiments, the phosphorus material functions as ananode active material.

The amount of the phosphorus material contained in the anode material isnot particularly limited and may be appropriately determined dependingon desired battery performance. For example, the content of thephosphorus material may be 10 mass % or more and 80 mass % or less ofthe total mass of the anode material. The lower limit of the content maybe 15 mass % or more, 20 mass % or more, or 25 mass % or more. The upperlimit of the content may be 70 mass % or less, or it may be 60 mass % orless. If the content of the phosphorus material is too large, the ionconductivity and electron conductivity of the anode layer of the lithiumion secondary battery may be insufficient.

2. C Element

The anode material contains a C element.

The C element derives from the carbon material used as a raw material.The carbon material is not particularly limited, as long as it is amaterial containing a C element. As the carbon material, examplesinclude, but are not limited to, vapor-grown carbon fiber (VGCF),acetylene black, activated carbon, furnace black, carbon nanotube,Ketjen Black and graphene. As the carbon material, a mixture of two ormore kinds of carbon materials may be used.

The carbon material functions as a conductive additive to increase theelectron conductivity of the anode material.

The amount of the carbon material contained in the anode material is notparticularly limited and may be appropriately determined depending ondesired battery performance. For example, the content of the carbonmaterial may be 5 mass % or more and 50 mass % or less of the total massof the anode material. The lower limit of the content may be 30 mass %or more. The upper limit of the content may be 40 mass % or less. If thecontent of the carbon material is too large, the content of thephosphorus material is relatively small, and the capacity of the anodematerial may be insufficient.

3. Li Element

The anode material may further contain a Li element. The Li elementderives from the lithium material used as a raw material. The lithiummaterial is not particularly limited, as long as it is a materialcontaining a Li element. As the lithium material, examples include, butare not limited to, Li₂S, Li₂O, LiF, LiCl, LiBr, LiI and Li_(x)MO_(y)(where x and y are positive numbers, and M is P, Si, Ge, B, Al, Ga orIn).

The amount of the lithium material contained in the anode material isnot particularly limited and may be appropriately determined dependingon desired battery performance.

4. S Element

The anode material may further contain an S element. The S elementderives from the sulfur material used as a raw material. The sulfurmaterial is not particularly limited, as long as it is a materialcontaining an S element. As the sulfur material, examples include, butare not limited to P₂S₅, GeS₂, SiS₂ and B₂S₃.

The amount of the sulfur material contained in the anode material is notparticularly limited and may be appropriately determined depending ondesired battery performance.

5. Li Element and S Element

Since the reversible capacity of the lithium ion secondary battery canbe further increased, the anode material may contain both the Li elementand the S element. The Li element and the S element may derive from amixture of the lithium material and the sulfur material, or they mayderive from the lithium-sulfur material.

The lithium-sulfur material is not particularly limited, as long as itcontains both the Li element and the S element. As the lithium-sulfurmaterial, a material known to function as a solid electrolyte, may beused. As the lithium-sulfur material, examples include, but are notlimited to, Li₂S, Li₂S—P₂S₅, Li₂S—P₂S₅—LiI, Li₂S—P₂S₅—GeS₂,Li₂S—P₂S₅—Li₂O, Li₂S—P₂S₅—Li₂O—LiI, Li₂S-P₂S₅—LiI—LiBr, Li₂S—SiS₂,Li₂S—SiS₂—LiI, Li₂S—SiS₂—LiBr, Li₂S—S—SiS₂—LiCl, Li₂S—S—SiS₂—B₂S₃—LiI,Li₂S—S—SiS₂—P₂S₅—LiI, Li₂S—B₂S₃, Li₂S-P₂S₅—ZnSn (where m and n arepositive numbers, and Z is Ge, Zn or Ga), Li₂S—GeS₂, Li₂S—S—SiS₂—Li₃PO₄,and Li₂S—S—SiS₂—Li_(x)MO_(y) (where x and y are positive numbers, and Mis P, Si, Ge, B, Al, Ga or In).

These lithium-sulfur materials may be used solely or in combination oftwo or more. In the case of using two or more lithium-sulfur materials,they may be nixed.

The amount of the mixture of the lithium material and sulfur materialcontained in the anode material or the amount of the lithium-sulfurmaterial contained therein is not particularly limited and may beappropriately determined depending on desired battery performance. Forexample, the content of the mixture or the lithium-sulfur material naybe 10 mass % or more and 80 mass % or less of the total mass of theanode material. The lower limit of the content nay be 15 mass % or more,20 mass % or more, or 30 mass % or more. The upper limit of the contentmay be 70 mass % or less, or 60 mass % or less. If the content of themixture or the lithium-sulfur material is too large, the content of thephosphorus material is relatively small, and the capacity of the anodematerial may be insufficient.

6. Others

As needed, the anode material of the disclosed embodiments may containother materials such a binder.

As the binder, examples include, but are not limited to,acrylonitrile-butadiene rubber (ABR), butadiene rubber (BR),polyvinylidene fluoride (PVdF) and styrene-butadiene rubber (SBR). Thecontent of the binder in the anode material is not particularly limited.

7. Anode Material

7-1. State of Anode Material

The state of the anode material may be an amorphous state. For example,the anode material is determined to be in the amorphous state when adiffraction peak is not present in a range of 2::=10 é to 30 é of aspectrum obtained by X-ray diffraction (XRD) measurement. Also, theanode material is determined to be in the amorphous state when there isno peak in a range of from 300 cm¹ to 500 cm¹ of its spectrum obtainedby Raman spectroscopy measurement.

7-2. Dispersibility of Anode Material

The dispersibility of the anode material may be evaluated by thefollowing method, for example.

Energy dispersive X-ray spectroscopy (EDS) elemental mapping is carriedout in the following measurement condition: an accelerating voltage of15 kV and PK one line. Accordingly, a scanning electron microscope (SEM)image at 3000-fold magnification (aspect ratio 3:4) is obtained. For theSEM image, the P element and other elements (such as the C, S and Lielements) are multi-valued, and 10 vertical lines and 10 horizontallines are drawn on the image at regular intervals. The total of thenumber of times the lines pass through an area corresponding to the Pelement, may be used as the index of the dispersibility (dispersionindex) to evaluate the dispersibility of the anode material.

For the dispersion index of the anode material calculated from the SEMimage obtained by the EDS elemental mapping, the lower limit may be 501or more or may be 1000 or more, and the upper limit is not particularlylimited.

7-3. Intended Applications of Anode Material

The anode material of the disclosed embodiments is used in a lithium ionsecondary battery. As the lithium ion secondary battery, examplesinclude, but are not limited to, an aqueous lithium ion secondarybattery, a non-aqueous lithium ion secondary battery and anall-solid-state lithium ion secondary battery. The term ‘secondarybattery encompasses the use of the secondary battery as a primarybattery (i.e., the case where the secondary battery is charged anddischarged only once).

B. Method for Producing Anode Material

According to the disclosed embodiments, a method for producing an anodematerial for lithium ion secondary batteries is provided, the methodcomprising preparing a phosphorus material and a carbon material, andamorphizing the phosphorus material and the carbon material.

(1) Preparing

This is a step of preparing a phosphorus material and a carbon material.

In the preparing, a first raw material composition containing thephosphorus material and the carbon material may be prepared by mixingthe phosphorus material and the carbon material.

That is, in the preparing, the phosphorus material and the carbonmaterial may be separately prepared, or they may be nixed and preparedas the first raw material composition. The method for mixing thephosphorus material and the carbon material to prepare the first rawmaterial composition, is not particularly limited. For example, they maybe mixed by use of a mortar.

As the phosphorus material and the carbon material, examples include,but are not limited to, the phosphorus materials and carbon materialsprovided above in ‘A. Anode material.

In the preparing, as needed, at least one selected from the groupconsisting of a lithium material, a sulfur material and a lithium-sulfurmaterial may be further prepared. In this case, in the preparing, asecond raw material composition containing the phosphorus material, thecarbon material and the at least one selected from the group consistingof the lithium material, the sulfur material and the lithium-sulfurmaterial, may be prepared by mixing the phosphorus material, the carbonmaterial, and the at least one selected from the group consisting of thelithium material, the sulfur material and the lithium sulfur material.

That is, in the preparing, the phosphorus material, the carbon materialand the at least one selected from the group consisting of the lithiummaterial, the sulfur material and the lithium sulfur material may beseparately prepared, or they may be mixed and prepared as the second rawmaterial composition. The method for mixing the phosphorus material, thecarbon material and the at least one selected from the group consistingof the lithium material, the sulfur material and the lithium sulfurmaterial to prepare the second raw material composition, is notparticularly limited. For example, they may be mixed by use of a mortar.

As the lithium material, the sulfur material and the lithium sulfurmaterial, examples include, but are not limited to, the lithiummaterials, sulfur materials and lithium sulfur materials provided abovein ‘A. Anode material,

(2) Amorphizing

This is a step of amorphizing the phosphorus material and the carbonmaterial. In the preparing, when at least one selected from the groupconsisting of a lithium material, a sulfur material and a lithium sulfurmaterial is further prepared as a raw material for the anode material,in addition to the phosphorus material and the carbon material, the atleast one selected from the group consisting of the lithium material,the sulfur material and the lithium sulfur material, may be amorphizedin the amorphizing.

By the amorphizing, the raw materials for the anode material areamorphized, and the dispersibility of the thus-obtained anode materialis increased. As a result, the reversible capacity of the lithium ionsecondary battery comprising the anode material, is increased.

In the amorphizing, at least the phosphorus material and carbon materialprepared in the above-mentioned preparing, which are raw materials forthe anode material, may be amorphized, and the amorphization of the rawmaterials is carried out by a conventionally-known method such asmechanical milling and melt-quenching. From the viewpoint of productioncost reduction, mechanical milling may be used.

The raw materials are determined to be in the amorphous state by, forexample, the presence or absence of a diffraction peak in a range of2::=10 é to 30 é of the spectrum obtained by the X-ray diffraction (XRD)measurement, and by the presence or absence of a peak in a range of from300 cm¹ to 500 cm¹ of the spectrum obtained by Raman spectroscopymeasurement.

When the mechanical milling is carried out in the amorphizing, themechanical milling may be carried out on the first raw materialcomposition containing the phosphor us material and the carbon materialin one step, or it may be carried out as follows: after the mechanicalmilling is carried out on one of the raw materials (the phosphorusmaterial and the carbon material), the other raw material is addedthereto, and then the mechanical milling is carried out on the mixture.

From the viewpoint of reducing the production cost of the lithium ionsecondary battery, the mechanical milling may be carried out on thefirst raw material composition in one step.

When at least one selected from the group consisting of a lithiummaterial, a sulfur material and a lithium-sulfur material is furtherprepared as a raw material in the preparing and mechanical milling iscarried out in the amorphizing, the mechanical milling may be carriedout in one step at the predetermined grinding energy on the second rawmaterial composition containing the phosphor us material, the carbonmaterial and the at least one selected from the group consisting of thelithium material, the sulfur material and the lithium sulfur material,or the mechanical milling may be carried out as follows: the rawmaterials are added in sequence, and the mechanical milling is carriedout in several steps at the predetermined grinding energy. In this case,the order of carrying out the mechanical milling on the raw materials,does not natter.

From the viewpoint of reducing the production cost of the lithium ionsecondary battery, the mechanical milling may be carried out on thesecond raw material composition in one step.

The mechanical milling is not particularly limited, as long as it is amethod of milling the raw materials or the raw material composition byapplying mechanical energy. The mechanical milling may be carried out bya ball mill, a vibrating mill, a turbo mill, mechanofusion, a disk millor the like. From the viewpoint of ease of the amorphization of the rawmaterials or the raw material composition, a planetary ball mill may beused.

The mechanical milling uses a grinding medium. As the raw material forthe grinding medium examples include, but are not limited to, ceramics,glass and metal.

The mechanical milling nay be dry or wet mechanical milling. Wetmechanical milling uses a liquid, and the liquid is not particularlylimited. When at least one selected from the group consisting of thesulfur material and the lithium sulfur material, is contained as amaterial to be subjected to the mechanical milling, the liquid may be aliquid which is aprotic to the extent that does not generate hydrogensulfide. As the liquid, examples include, but are not limited to,aprotic liquids such as a polar aprotic liquid and a non-polar aproticliquid.

A rotor is used to stir the grinding medium disposed inside thecontainer of the mechanical milling device. The rim speed of the rotornay be in a range of from 5 m/s to 2000 m/s, or in a range of from 628m/s to 1571 m/s, for example. In general, the rim speed of the rotormeans the rim speed of the outer rim of the rotor.

The grinding energy applied to the raw materials or the raw materialcomposition by the mechanical milling device, is defined as follows:Grinding energyE=(mv ²/2)nt/swhere E is the grinding energy; m is the mass (kg) of each grindingmedium, v is the rim speed (m/s) of the rotor; n is the number of thegrinding medium, t is the mechanical milling time (sec); and s is themass (g) of the raw materials or the raw material composition.

From the viewpoint of efficiently amorphizing the raw materials or theraw material composition, the lower limit of the grinding energy may be3.07 B 10¹¹ kJ×sec/g or more. The upper limit of the grinding energy isnot particularly limited, and it may be 38.4 B 10¹¹ kJ×sec/g or less,for example.

The condition of the mechanical milling is appropriately determined toobtain the desired anode material. For example, in the case of using theplanetary ball mill, the raw materials or the raw material compositionand grinding balls are put in the container of the planetary ball mill,and the mechanical milling is carried out at a predetermined platerotational frequency for a predetermined time. For example, the platerotational frequency is 200 rpm or more, may be 300 rpm or more, or maybe 500 rpm or more. On the other hand, the plate rotational frequency is800 rpm or less, or it may be 600 rpm or less.

In the case of using the planetary ball mill, the mechanical millingtime is 30 minutes or more, for example, or it may be 5 hours or more.On the other hand, the mechanical milling time may be 100 hours or less,for example, or it may be 76 hours or less, or may be 38 hours or less.

As the material for the container and grinding balls used with theplanetary ball mill, examples include, but are not limited to, ZrO₂ andAl₂O₃.

The diameter of the grinding balls may be 1 mm or more and 20 mm orless, for example.

The mechanical milling may be carried out in an inert gas atmospheresuch as Ar gas atmosphere.

As needed, the raw material composition may contain other materials suchas a binder. The binder may be appropriately selected from the examplesof the binder contained in the anode material, which are provided abovein ‘A. Anode material.

The content of the mixture of the phosphorus material, carbon material,lithium material and sulfur material in the raw material composition orthe content of the lithium-sulfur material therein may be the same asthe content of the mixture of the phosphorus material, carbon material,lithium material and sulfur material in the anode material describedabove in ‘A. Anode material or the content of the lithium-sulfurmaterial in the anode material described above in ‘A. Anode material.

C. All-solid-state lithium ion secondary battery According to thedisclosed embodiments, an all-solid-state lithium ion secondary batterycomprising a cathode layer, an anode layer and a solid electrolyte layerdisposed between the cathode layer and the anode layer, wherein theanode layer contains the anode material, is provided.

FIG. 1 is a schematic sectional view of an example of an all-solid-statelithium ion secondary battery.

As shown in FIG. 1 , an all-solid-state lithium ion secondary battery100 comprises a cathode 16 comprising a cathode layer 12 and a cathodecurrent collector 14, an anode 17 comprising an anode layer 13 and ananode current collector 15, and a solid electrolyte layer 11 disposedbetween the cathode layer 12 and the anode layer 13.

The cathode layer is a layer containing at least a cathode activematerial.

The type of the cathode active material is not particularly limited, andany of materials applicable as the active material of theall-solid-state lithium ion secondary battery, may be used. As thecathode active material, examples include, but are not limited to, alithium (Li) metal, a lithium alloy, LiCoO₂, LiNi_(x)Co_(1-x)O₂ (0<x<1),LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂, LiMnO₂, a different element-substitutedLi—Mn spinel (such as LiMn_(1.5)Ni_(0.5)O₄, LiMn_(1.5)Al_(0.5)O₄,LiMn_(1.5)Mg_(0.5)O₄, LiMn_(1.5)Co_(0.5)O₄, LiMn_(1.5)Fe_(0.5)O₄ andLiMn_(1.5)Zn_(0.5)O₄,), a lithium titanate (such as Li₄Ti₅O₁₂), alithium metal phosphate (such as LiFePO₄, LiHMnPO₄, LiCoPO₄ andLiNiPO₄), a lithium compound such as LiCoN, Li₂SiO₃ and Li₄SiO₄, atransition metal oxide (such as V₂O₅ and MoO₃), TiS₂, P, Si, SiO₂ and alithium storage intermetallic compound (such as Mg₂Sn, Mg₂Ge, Mg₂Sb andCu₃Sb). As the lithium alloy, examples include, but are not limited to,Li—Au, Li—Mg, Li—Sn, Li—Si, Li—Al, Li—B, Li—C, Li—Ca, Li—Ga, Li—Ge,Li—As, Li—Se, Li—Ru, Li—Rh, Li—Pd, Li—Ag, Li—Cd, Li—In, Li—Sb, Li—Ir,Li—Pt, Li—Hg, Li—Pb, Li—Bi, Li—Zn, Li—Tl, Li—Te and Li—At.

The form of the cathode active material is not particularly limited. Thecathode active material may be in a particulate form.

A coat layer containing a Li ion-conducting oxide nay be formed on thesurface of the cathode active material, since a reaction between thecathode active material and the solid electrolyte is suppressed.

As the Li ion-conducting oxide, examples include, but are not limitedto, LiNbO₃, Li₄Ti₅O₁₂ and Li₃PO₄. The thickness of the coat layer is 0.1nm or more, for example, and it may be 1 nm or more. On the other hand,the thickness of the coat layer is 100 nm or less, for example, and itmay be 20 nm or less. Also, 70% or more of the surface of the cathodeactive material is coated with the coat layer, for example, and 90% ormore of the surface may be coated with the coat layer.

As needed, the cathode layer may contain at least one of a solidelectrolyte, a conductive additive and a binder. The solid electrolytemay be appropriately selected from the examples of the solid electrolytethat may be contained in the below-described solid electrolyte layer.The conductive additive may be appropriately selected from the examplesof the carbon material that may be contained in the anode materialdescribed above in ‘A. Anode material. The binder may be appropriatelyselected from the examples of the binder that may be contained in theanode material described above in ‘A. Anode material.

The thickness of the cathode layer is not particularly limited. Forexample, it may be 0.1≈m or more and 1000≈m or less.

The cathode layer is easily formed by pressing the cathode activematerial, etc., for example.

The anode layer comprises the above-described anode material.

The thickness of the anode layer is not particularly limited. Forexample, it nay be 0.1≈m or more and 1000≈m or less.

The anode layer is easily formed by pressing the above-described anodematerial, for example.

The solid electrolyte layer is a layer containing at least a solidelectrolyte. As needed, it may contain a binder.

As the solid electrolyte, examples include, but are not limited to, asulfide solid electrolyte, an oxide solid electrolyte, a nitride solidelectrolyte and a halide solid electrolyte. The solid electrolyte may bea sulfide solid electrolyte.

The sulfide solid electrolyte may contain a Li element, an A element (Ais at least one of P, Ge, Si, Sn, B and Al) and an S element. Thesulfide solid electrolyte may further contain a halogen element. As thehalogen element, examples include, but are not limited to, an F element,a Cl element, a Br element and an I element. The sulfide solidelectrolyte may further contain an O element.

As the sulfide solid electrolyte, examples include, but are not limitedto, Li₂S—P₂S₅, Li₂S—P₂S₅—LiI, Li₂S—P₂S₅—GeS₂, Li₂S—P₂S₅—Li₂O,Li₂S—P₂S₅—Li₂O—LiI, Li₂S—P₂S₅—LiI—LiBr, Li₂S—S—SiS₂. Li₂S—S—SiS₂—LiI,Li₂S—S—SiS₂—LiBr, Li₂S—S—SiS₂—LiCl, Li₂S—S—SiS₂-B₂S₃—LiI,Li₂S—S—SiS₂—P₂S₅—LiI, Li₂S—B₂S₃, Li₂S—P₂S₅—ZnSn (where m and n arepositive numbers, and Z is Ge, Zn or Ga), Li₂S-GeS₂, Li₂S—S—SiS₂—Li₃PO₄and Li₂S—S—SiS₂—Li (where x and y are positive numbers, and M is P, Si,Ge, B, Al, Ga or In).

These solid electrolytes may be used solely or in combination of two ormore. In the case of using two or more solid electrolytes, they may bemixed, or they may be formed into layers to form a multilayer structure.

The amount of the solid electrolyte contained in the solid electrolytelayer, is not particularly limited. For example, it may be 50 volume %or more, may be 70 volume % or more, or may be 90 volume % or more. Thebinder used in the solid electrolyte layer may be appropriately selectedfrom the examples of the binder that may be contained in the anodematerial described above in ‘A. Anode material.

The thickness of the solid electrolyte layer is not particularly United.For example, it may be 0.1≈m or more and 1000≈m or less. The solidelectrolyte layer is easily formed by pressing the above-described solidelectrolyte, etc., for example.

As the material for the cathode current collector, examples include, butare not limited to, SUS, aluminum, nickel, iron, titanium and carbon. Asthe material for the anode current collector, examples include, but arenot limited to, SUS, copper, nickel and carbon.

The form of the cathode current collector and the anode currentcollector may be a foil form or a mesh form, for example.

As needed, the all-solid-state lithium ion secondary battery comprisesan outer casing for housing the cathode, the anode and the solidelectrolyte layer.

The material for the outer casing is not particularly United, as long asit is a material stable in electrolytes. As the material, examplesinclude, but are not limited to, metals and resins such aspolypropylene, polyethylene and acrylic resins.

As the form of the all-solid-state lithium ion secondary battery,examples include, but are not limited to, a coin form, a laminate form acylindrical form and a square form.

The method for producing the all-solid-state lithium ion secondarybattery of the disclosed embodiments, is not particularly limited. Itmay be a conventionally-known method.

EXAMPLES Example 1

[Production of Anode Material Containing P and C elements]

[Preparing]

Red phosphorus and acetylene black were prepared as a phosphorusmaterial and a carbon material, respectively, which were raw materialsfor the anode material. The phosphorus material and the carbon materialwere weighed in a mass ratio of 4:3. The raw materials were mixed in anagate mortar for 15 minutes, thereby obtaining a first raw materialcomposition (1.75 g).

[Amorphizing]

The first raw material composition was put in the container (made ofZrO₂, 45 cc) of a planetary ball mill. In addition, 500 ZrO₂ balls(diameter 4 mm, 57 g) were put in the container. Then, the container washermetically closed. The container was installed in the planetary ballmill (‘P7 manufactured by FRITSCH). Mechanical milling for one hour(plate rotational frequency 500 rpm, rotor rim speed 1571 m/s, grindingenergy 2.74 B 10¹² kJ×sec/g), suspension for 15 minutes, mechanicalmilling in reverse rotation for one hour (plate rotational frequency 500rpm) and another suspension for 15 minutes were considered as one cycle,and this cycle was repeated to carry out a total of 38 hours ofmechanical milling. Accordingly, the anode material containing P and Celements of Example 1 was obtained.

[Production of Evaluation Cell]

As a solid electrolyte, 100 mg of (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBrwas put in a 1 cm² ceramics mold and pressed at 1 ton/cm² to obtain asolid electrolyte layer. Then, 8 mg (weight per unit area: 8 mg/cm²) ofthe anode material containing the P and C elements was placed on oneside of the layer and pressed at 6 ton/cm² to produce a workingelectrode. On the other side of the layer, a lithium-indium alloy foilwas disposed as a counter electrode. They were pressed at 1 ton/cm²,thereby obtaining the evaluation battery of Example 1.

Comparative Example 1

The anode material containing P and C elements of Comparative Example 1was obtained in the same manner as Example 1, except that theamorphizing was not carried out. Then, the evaluation battery ofComparative Example 1 was obtained in the same manner as Example 1.

Example 2

[Production of Anode Material Containing P, C, Li and S Elements]

[Preparing]

Red phosphorus, acetylene black and (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBrwere prepared as a phosphorus material, a carbon material and alithium-sulfur material, respectively, which were raw materials for theanode material. The phosphorus material, the lithium-sulfur material andthe carbon material were weighed in a mass ratio of 4:3:3. The rawmaterials were mixed in an agate mortar for 15 minutes, therebyobtaining a second raw material composition (2.5 g).

[Amorphizing]

The second raw material composition was put in the container (made ofZrO₂, 45 cc) of the planetary ball mill. In addition, the 500 ZrO₂ balls(diameter 4 mm, 57 g) were put in the container. Then, the container washermetically closed. The container was installed in the planetary ballmill (‘P7 manufactured by FRITSCH). Mechanical milling for one hour(plate rotational frequency 500 rpm, rotor rim speed 1571 m/s, grindingenergy 1.92 B 10¹² kJ×sec/g), suspension for 15 minutes, mechanicalmilling in reverse rotation for one hour (plate rotational frequency 500rpm) and another suspension for 15 minutes were considered as one cycle,and this cycle was repeated to carry out a total of 38 hours ofmechanical milling. Accordingly, the anode material containing P, C, Liand S elements of Example 2 was obtained.

[Production of Evaluation Battery]

As a solid electrolyte, 100 mg of (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBrwas put in the 1 cm² ceramics mold and pressed at 1 ton/cm² to obtain asolid electrolyte layer. Then, 8 mg (weight per unit area: 8 mg/cm²) ofthe anode material containing the P, C, Li and S elements was placed onone side of the layer and pressed at 6 ton/cm² to produce a workingelectrode. On the other side of the layer, a lithium-indium alloy foilwas disposed as a counter electrode. They were pressed at 1 ton/cm²,thereby obtaining the evaluation battery of Example 2.

Comparative Example 2

The anode material containing P, C, Li and S elements of ComparativeExample 2 was obtained in the same manner as Example 2, except that theamorphizing was not carried out. Then, the evaluation battery ofComparative Example 2 was obtained in the same manner as Example 2.

Example 3

The anode material containing P, C, Li and S elements of Example 3 wasobtained in the same manner as Example 2, except that in the preparing,VGCF was used as the carbon material, in place of acetylene black. Then,the evaluation battery of Example 3 was obtained in the same manner asExample 2.

Example 4

The anode material containing P, C, Li and S elements of Example 4 wasobtained in the same manner as Example 2, except that in theamorphizing, the mechanical milling condition was changed as follows:the plate rotational frequency was changed to 200 rpm, the rotor rimspeed was changed to 628 m/s; and the grinding energy was changed to3.07 B 10¹¹ kJ×sec/g or more. Then, the evaluation battery of Example 4was obtained in the same manner as Example 2.

Example 5

The anode material containing P, C, Li and S elements of Example 5 wasobtained in the same manner as Example 2, except that in theamorphizing, the mechanical milling condition was changed as follows:the plate rotational frequency was changed to 300 rpm, the rotor rimspeed was changed to 942 m/s; and the grinding energy was changed to6.91 B 10¹¹ kJ×sec/g. Then, the evaluation battery of Example 5 wasobtained in the same manner as Example 2.

Example 6

The anode material containing P, C, Li and S elements of Example 6 wasobtained in the same manner as Example 2, except that in theamorphizing, the mechanical milling condition was changed as follows:the plate rotational frequency was changed to 400 rpm, the rotor rimspeed was changed to 1257 m/s; and the grinding energy was changed to1.23 B 10¹² kJ×sec/g. Then, the evaluation battery of Example 6 wasobtained in the same manner as Example 2.

Comparative Example 3

The anode material containing P, C, Li and S elements of ComparativeExample 3 was obtained in the same manner as Example 2, except that inthe amorphizing, the mechanical milling condition was changed asfollows: the plate rotational frequency was changed to 100 rpm, therotor rim speed was changed to 314 m/s; and the grinding energy waschanged to 0.76 B 10¹¹ kJ×sec/g. Then, the evaluation battery ofComparative Example 3 was obtained in the same manner as Example 2.

Example 7

[Production of Anode Material Containing P, C, Li and S Element s]

[Preparing]

Red phosphorus, acetylene black and (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBrwere prepared as a phosphorus material, a carbon material and alithium-sulfur material, respectively, which were raw materials for theanode material. The phosphorus material, the lithium-sulfur material andthe carbon material were weighed in a mass ratio of 4:3:3 so that themass of a second raw material composition to be obtained was 2.5 g.

[Amorphizing]

First, a mixture of the carbon material and the lithium-sulfur materialwas put in the container (made of ZrO₂, 45 cc) of the planetary ballmill. In addition, the 500 ZrO₂ balls (diameter 4 mm, 57 g) were put inthe container. Then, the container was hermetically closed. Thecontainer was installed in the planetary ball mill (‘P7 manufactured byFRITSCH). Mechanical milling for one hour (plate rotational frequency500 rpm, rotor rim speed 1571 m/s, grinding energy 1.92 B 10¹²kJ×sec/g), suspension for 15 minutes, mechanical milling in reverserotation for one hour (plate rotational frequency 500 rpm) and anothersuspension for 15 minutes were considered as one cycle, and this cyclewas repeated to carry out a total of 38 hours of mechanical milling.

Then, the phosphorus material was further added to and mixed with themixture in the container, thereby obtaining the second raw materialcomposition. The container was hermetically closed again. The containerwas installed in the planetary ball mil (‘P7 manufactured by FRITSCH)again. Mechanical milling for one hour (plate rotational frequency 500rpm, rotor rim speed 1571 m/s, grinding energy 1.92 B 10¹² kJ×sec/g),suspension for 15 minutes, mechanical milling in reverse rotation forone hour (plate rotational frequency 500 rpm) and another suspension for15 minutes were considered as one cycle, and this cycle was repeated tocarry out a total of 38 hours of mechanical milling again. Accordingly,the anode material containing P, C, Li and S elements of Example 7 wasobtained.

[Production of Evaluation Battery]

The evaluation battery of Example 7 was obtained in the same manner asExample 2.

Example 8

[Production of Anode Material Containing P, C, Li and S Elements]

[Preparing]

Red phosphorus, acetylene black and (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBrwere prepared as a phosphorus material, a carbon material and alithium-sulfur material, respectively, which were raw materials for theanode material. The phosphorus material, the lithium-sulfur material andthe carbon material were weighed in a mass ratio of 4:3:3 so that themass of a second raw material composition to be obtained was 2.5 g.

[Amorphizing]

First, the phosphorus material was put in the container (nude of ZrO₂,45 cc) of the planetary ball mill. In addition, the 500 ZrO₂ balls(diameter 4 mm, 57 g) were put in the container. Then, the container washermetically closed. The container was installed in the planetary ballmill (‘P7 manufactured by FRITSCH). Mechanical milling for one hour(plate rotational frequency 500 rpm, rotor rim speed 1571 m/s, grindingenergy 1.92 B 10¹² kJ×sec/g), suspension for 15 minutes, mechanicalmilling in reverse rotation for one hour (plate rotational frequency 500rpm) and another suspension for 15 minutes were considered as one cycle,and this cycle was repeated to carry out a total of 38 hours ofmechanical milling.

Then, the carbon material and the lithium-sulfur material were furtheradded to and mixed with the phosphorus material in the container,thereby obtaining the second raw material composition. The container washermetically closed again. The container was installed in the planetaryball mill (‘P7 manufactured by FRITSCH) again. Mechanical milling forone hour (plate rotational frequency 500 rpm, rotor rim speed 1571 m/s,grinding energy 1.92 B 10¹² kJ×sec/g), suspension for 15 minutes,mechanical milling in reverse rotation for one hour (plate rotationalfrequency 500 rpm) and another suspension for 15 minutes were consideredas one cycle, and this cycle was repeated to carry out a total of 38hours of mechanical milling again. Accordingly, the anode materialcontaining P, C, Li and S elements of Example 8 was obtained.

[Production of Evaluation Battery]

The evaluation battery of Example 8 was obtained in the same manner asExample 2.

TABLE 1 Grinding Reversible Presence Composition energy capacity orabsence (molar ratio) (kj Xsec/g) (mAh/g-P) of peak DispersibilityExample 1 P₁₂₈₄₀C₃₆₀₃ 2.74 B 10¹² 1891 Absent A Example 2Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 1.92 B 10¹² 2278 Absent A Example 3Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 1.92 B 10¹² 2570 Absent A Example 4Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 3.07 B 10¹¹ 2503 Absent B Example 5Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 6.91 B 10¹¹ 2485 Absent B Example 6Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 1.23 B 10¹² 2724 Absent A Example 7Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 3.84 B 10¹² 2539 Absent A Example 8Li_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 3.84 B 10¹² 2357 Absent B ComparativeP₁₂₈₄₀C₃₆₀₃ 0 52 Present C Example 1 ComparativeLi_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 0 214 Present C Example 2 ComparativeLi_(4.5)P₁₂₈₄₁S_(5.1)C₃₆₀₃ 0.76 B 10¹¹ 65 Present C Example 3[XRD Measurement]

XRD measurement was carried out on the anode materials of Examples 1 to8 and Comparative Examples 1 to 3, the black phosphorus, the redphosphorus, the lithium-sulfur material(75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr) and the acetylene black (AB).

FIG. 2 is a view showing the XRD patterns of the anode material ofExample 2, the anode material of Comparative Example 2, the blackphosphorus, the red phosphorus, the lithium-sulfur material(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr) and the acetylene black (AB). Table 1shows the presence or absence of a diffraction peak in a range of 2::=10é to 30 é for the anode materials of Examples 1 to 8 and ComparativeExamples 1 to 3. Like the anode material of Example 2 shown in FIG. 2 ,the anode material showing no diffraction peak can be said to be anamorphized anode material. Meanwhile, it is clear that like the anodematerial of Comparative Example 2 shown in FIG. 2 , the anode materialshowing the diffraction peak is not an amorphized anode material, sincea similar diffraction peak to the XRD patterns of the red phosphorus andthe lithium-sulfur material (75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr), whichare raw materials, is observed.

[Raman Spectroscopy Measurement]

Raman spectroscopy measurement was carried out on the anode material ofExample 2, the anode material of Comparative Example 2, the blackphosphorus, the red phosphorus and the lithium-sulfur material(75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr).

FIG. 3 is a view showing the Raman spectra of the anode material ofExample 2, the anode material of Comparative Example 2, the blackphosphorus, the red phosphorus and the lithium-sulfur material(75(0.75Li₂S×0.25P₂S₅)×10LiI×15LiBr). For the anode material ofComparative Example 2, a peak derived from the red phosphorus and theframework of PS₄ ³⁻ is present in a range of from 300 cm¹ to 500 cm¹.For the anode material of Example 2, it is clear that there is no peakderived from them. This fact is not inconsistent with the XRDmeasurement results and shows that by the presence or absence of a peakin a range of from 300 cm¹ to 500 cm¹ of the Raman spectrum, it can bedetermined whether or not the anode material is in the amorphous statedescribed in the disclosed embodiments.

[EDS]

SEM EDS elemental analysis was carried out on the anode material ofExample 2 and the anode material of Comparative Example 2.

FIG. 4 is a secondary electron image (a SEM image) of the anode materialof Example 2. FIG. 5 is a backscattered electron image (a BF image) ofthe anode material of Example 2.

FIG. 6 is a secondary electron image (a SEM image) of the anode materialof Comparative Example 2. FIG. 7 is a backscattered electron image (a BFimage) of anode material of Comparative Example 2.

From the SEM image of the anode material of Comparative Example 2 shownin FIG. 6 , the presence of a particle 5≈m or more in size, wasconfirmed. From the BF image of the anode material of ComparativeExample 2 shown in FIG. 7 , the particle is different in contrast fromother areas. From these facts, it is clear that the composition of theanode material of Comparative Example 2 is present in a non-uniformlydistributed manner.

From the SEM image of the anode material of Example 2 shown in FIG. 4 ,the presence of a particle 5≈m or more in size, was confirmed as well.From the BF image of the anode material of Example 2 shown in FIG. 5 ,it is clear that there is no contrast and the composition of the anodematerial is uniform

[Dispersibility]

EDS elemental mapping was carried out on the anode material of Example 2and the anode material of Comparative Example 2.

Dispersibility evaluation was carried out based on a difference incontrast between images obtained by the EDS elemental mapping. Morespecifically, the EDS mapping was carried out in the followingmeasurement condition: an accelerating voltage of 15 kV and PK one line.Accordingly, scanning electron microscope (SEM images at 3000-foldmagnification (aspect ratio 3:4) were obtained. For each SEM image, theP element and other elements were multi-valued, and 10 vertical linesand 10 horizontal lines were drawn on the image at regular intervals.The total of the number of times the lines passed through an areacorresponding to the P element, was used as the index of thedispersibility (dispersion index) to evaluate the dispersibility of theanode material.

FIG. 8 is an image obtained by EDS mapping of the anode material ofExample 2. FIG. 9 is an image obtained by EDS mapping of the anodematerial of Comparative Example 2.

FIG. 9 shows that for Comparative Example 2, the number of times thevertical lines passed through the area corresponding to the P element,is 40; the number of times the horizontal lines passed through the areacorresponding to the P element, is 53; and the dispersion index is 93.FIG. 8 shows that for Example 2, the number of times the vertical linespassed through the area corresponding to the P element, is 550 or more;the number of times the horizontal lines passed through the areacorresponding to the P element, is 1100 or more; and the dispersionindex is 1650 or more.

The dispersibility evaluation results are shown in Table 1. In Table 1,a dispersion index of from 1 to 500 was evaluated as poor dispersibilityand ‘C; a dispersion index of from 501 to 1000 was evaluated as gooddispersibility and ‘B; and a dispersion index of more than 1000 wasevaluated as very good dispersibility and ‘A. From Table 1, it is clearthat the anode materials of Examples 1 to 8 have high dispersibility.This is considered be because, since the anode materials were in theamorphous state, the dispersibility of the anode materials of Examples 1to 8 was increased.

[Battery Characteristics Evaluation]

A charge-discharge test was carried out for 3 cycles on the evaluationbattery obtained in Example 1, in the following condition; a temperatureenvironment of 60éC, a current value of 0.5 (mA/cm²) and a voltage rangeof from 0 V (vs. Li/Li⁺) to 1.5 V (vs. Li/Li⁺).

In the same manner as the evaluation battery obtained in Example 1, thecharge-discharge test was carried out on the evaluation batteriesobtained in Examples 2 to 8 and Comparative Examples 1 to 3. Thecapacity calculated from the charge and discharge of the second cycle ofeach evaluation battery, was determined as reversible capacity. Thereversible capacities of the evaluation batteries are shown in Table 1.

FIG. 10 is a view showing the charge-discharge curves of the evaluationbattery of Example 2. FIG. 11 is a view showing the charge-dischargecurves of the evaluation battery of Comparative Example 2. It is clearthat while the evaluation battery of Comparative Example 2 obtained thecapacity by initial discharge, almost no reversible capacity wasobtained. Meanwhile, it is clear that the evaluation battery of Example2 is large in initial discharge capacity and reversible capacity. Asshown in Table 1, it is clear that the evaluation batteries of Examples1 to 8 are large in reversible capacity compared to the evaluationbatteries of Comparative Examples 1 to 3. The reason is considered asfollows: since the anode materials used in the evaluation batteries ofExamples 1 to 8 were in the amorphous state, the dispersibility of thephosphorus and carbon was increased, and due to the increase in thedispersibility, the conductive path in the anode materials was optimizedto increase the reversible capacity of the evaluation batteries.

As shown in Table 1, the evaluation battery of Example 2 is larger thanthe reversible capacity of the evaluation battery of Example 1. Thereare possible reasons for this. Since the lithium-sulfur materialcontaining the Li and S elements and having a solid electrolytefunction, is included in the raw materials for the anode material, theconductive path in the anode material was optimized, the lithium waspre-doped with the phosphorus, or the P was highly dispersed in thematrix of the lithium-sulfur material, and expansion and contraction,which were attributed to charge and discharge, were suppressed, therebyincreasing the reversible capacity of the evaluation battery.

REFERENCE SIGNS LIST

-   11. Solid electrolyte layer-   12. Cathode layer-   13. Anode layer-   14. Cathode current collect or-   15. Anode current collect or-   16. Cathode-   17. Anode-   100. All-solid-state lithium ion secondary battery

The invention claimed is:
 1. A method for producing an anode materialfor lithium ion secondary batteries, the method comprising preparing araw material composition containing a phosphorus material, a carbonmaterial and a lithium-sulfur material by mixing the phosphorusmaterial, the carbon material and the lithium-sulfur material, andamorphizing the raw material composition by carrying out mechanicalmilling on the raw material composition at a grinding energy of3.07×10¹¹ kJ·sec/g or more and 38.4×10¹¹ kJ·sec/g or less.
 2. The methodfor producing the anode material for lithium ion secondary batteriesaccording to claim 1, wherein the mechanical milling is conducted for atime of 5 hours or more and 100 hours or less.
 3. The method forproducing the anode material for lithium ion secondary batteriesaccording to claim 1, wherein the mechanical milling is conducted for atime of 38 hours.
 4. The method for producing the anode material forlithium ion secondary batteries according to claim 1, wherein thephosphorus material is red phosphorus, wherein the carbon material isvapor-grown carbon fiber or acetylene black, and wherein thelithium-sulfur material is (75(0.75Li₂S.0.25P₂S₅)·10LiI.15LiBr.